Protective clothing such as protective suits for resisting gaseous and/or liquid noxious and/or odorous substances may be made from a range of different kinds of material. For example, EP-B-0 118 618 discloses flexible sheet materials which are suitable for making protective clothing, as well as a process for the production of such materials. The flexible sheet material to be found therein comprises an air-permeable carrier in web form, on which active particles which act on noxious and/or odorous substances and/or which react with same are fixed in a substantially uniform distribution by means of spaced-apart adhesive points or dots which in particular are applied to the carrier by a printing operation. Such a material can be produced by a procedure which involves applying spaced-apart adhesive points or dots by printing using a pattern or screen roller to a flexible air-permeable carrier web, with active particles being applied to the carrier web as long as the adhesive points or dots are still sticky, whereupon the particles are fixed to the carrier web with hardening of the adhesive. The carrier of the above-indicated material is a textile material while, as referred to above, the adhesive points or dots are applied to the carrier by printing using a roller in a rotary screen printing procedure.
It is however also possible for the carrier material used to be for example PU-foam, in which case then adhesive points or dots are normally not used for fixing the active particles on the carrier. Instead, the active particles are mixed with the adhesive to form a paste and the paste is then suitably applied to the foam carrier by a spreading process, for example using a brush.
The present invention is now more particularly concerned with an improvement in the sheet material having active particles in which the adhesive points are applied by being printed on the material carrier and then active particles are fixed to the adhesive points. With the adhesives which are generally used in that process however, a certain limit is set on the degree of fineness of the screen printing stencil used for producing the adhesive points on the carrier material, and that means that the spacing between the adhesive points is also subject to certain limitations. In general the usual adhesives can only be applied by printing using screen printing stencils down to a 30 mesh size, in order to prevent the adhesive dots from running together, which would thus result in the air-permeability of the carrier material being seriously reduced.
In that case, a plurality of active particles form a nested deposit on each adhesive point, and that results in regions in which there are no active particles occurring between adjacent adhesive points or nests of particles. In that situation, noxious and in particular toxic agents can flow through those regions without active particles, without being filtered and without being influenced, and that can have fatal consequences particularly if the material is to be used to afford protection from strong poisons.
That effect can have particularly dangerous consequences when the sheet material is used for protective clothing intended to provide protection from chemical warfare agents as, when the material is used for clothing, it is necessary to use suitably elastically stretchable carrier materials in order to guarantee the required mobility for the wearer of the protective suit. Particularly in the knee, elbow and buttocks regions, degrees of stretch of up to 50% may occur in such a situation, with the result that the spaces between the nests of particles are correspondingly considerably increased. That results in substantially greater permeability in regard to air and warfare agents and thus greatly reduces the protective effect of the suit, at least in some regions thereof.